Pump drive unit for battery operated fluid dispensers

A battery operated, handheld fluid dispenser comprises a supply container having a body portion and a narrow neck extending upwardly therefrom. A pump and discharge unit is mounted on the upper end of the neck and comprises a pump diaphragm and pump chamber for pumping liquid from the container to a discharge nozzle. A battery powered pump drive unit is mounted on the container and comprises an electric motor having an output shaft coupled with the pump diaphragm through a cam and cam follower arrangement to displace the diaphragm through a pump stroke when the motor is energized. The cam is rotatably driven by the motor, and the cam follower is attached to the diaphragm, whereby rotation of said cam axially displaces the diaphragm, and the cam and cam follower have interengaging dual cam faces for balancing lateral forces therebetween during rotation of said cam relative to said cam follower.